Method of measuring the relative frequency response of a photonic integrated chip and a photodetector

Abstract

The present disclosure provides a method for measuring relative frequency responses of a photonic integrated chip and a photodetector, comprising: in response to a sweep signal externally applied to a first modulation arm of a modulator, sweeping a first radio frequency signal loaded on the first modulation arm to obtain a plurality of first optical carriers modulated and output by the first modulation arm; in response to a second radio frequency signal of a fixed frequency externally applied to a second modulation arm of the modulator, obtaining a second optical carrier modulated and output by the second modulation arm; adjusting a bias point of a phase of the modulator by an external direct current voltage source, so that a difference between phase shifts generated by the first modulation arm and the second modulation arm is; according to the plurality of first optical carriers and the second optical carrier, a first predetermined function corresponding to the photodetector is used for processing to obtain a first frequency response; and according to the plurality of first optical carriers and the second optical carrier, a second predetermined function corresponding to the photonic integrated chip is used for processing to obtain a second frequency response.

Description

Technical Field

[0001] This disclosure relates to the technical field of measuring the frequency response characteristics of optoelectronic devices, and more specifically, to a method and apparatus for measuring the relative frequency response of photonic integrated chips and photodetectors. Background Technology

[0002] High-speed photonic integrated chips are crucial components in the field of optical communication. Frequency response, a key performance indicator of high-speed photonic integrated chips, largely determines the transmission rate achievable by the communication system.

[0003] Currently, the main methods for measuring the frequency response of photonic integrated chips are direct frequency sweep measurement, frequency-shifting heterodyne measurement, and spectroscopic methods. Direct frequency sweep measurement requires prior knowledge of the frequency response of either the modulator or the high-speed photodetector, and then subtracts the known device's frequency response from the measurement data to obtain the frequency response of the photonic integrated chip under test. Spectroscopic methods are limited by the resolution of spectrometers, making it difficult to measure frequency response characteristics below gigahertz. Measuring the frequency response characteristics of photonic integrated chips based on microwave photonics methods shifts the optical measurement to the electrical domain. However, most frequency-shifting heterodyne measurement methods share the same limitations as direct frequency sweep measurement: prior knowledge of the frequency response of one device is required, and then subtracting the known device's frequency response from the measurement data to obtain the frequency response of the other device under test. Therefore, there is an urgent need to develop a method and apparatus for simultaneously measuring the relative frequency response of photonic integrated chips and photodetectors, achieving high-resolution frequency response measurement while performing self-calibration. Summary of the Invention

[0004] To address at least one of the technical problems in the prior art, this disclosure provides a method and apparatus for measuring the relative frequency response of a photonic integrated chip and a photodetector, which can simultaneously measure the relative frequency response of the photonic integrated chip and the photodetector, achieving high resolution while performing self-calibration.

[0005] This disclosure provides a method for measuring the relative frequency response of a photonic integrated chip and a photodetector, wherein the photonic integrated chip includes a modulator. The method includes: in response to a sweep signal applied externally to a first modulation arm of the modulator, sweeping and outputting a first radio frequency signal loaded on the first modulation arm to obtain a plurality of first optical carriers modulated by the first modulation arm; in response to a second radio frequency signal of a fixed frequency applied externally to a second modulation arm of the modulator, obtaining a second optical carrier modulated by the second modulation arm; and adjusting the phase bias point of the modulator using an external DC voltage source so that the difference in phase shift generated by the first modulation arm and the second modulation arm is 1 / 2. Based on the frequency components of the beat frequency signals of the multiple first optical carriers and the multiple second optical carriers, a first frequency response is obtained by processing them using a first predetermined function corresponding to the photodetector; based on the frequency components of the beat frequency signals of the multiple first optical carriers and the multiple second optical carriers, a second frequency response is obtained by processing them using a second predetermined function corresponding to the photonic integrated chip.

[0006] According to some embodiments of this disclosure, the frequency of the first radio frequency signal applied to the first modulation arm is n times the frequency of the second radio frequency signal applied to the second modulation arm, where n is an integer not less than 1.

[0007] According to some embodiments of this disclosure, the phase bias point of the modulator is adjusted by an external DC voltage source so that the difference in phase shift between the first modulation arm and the second modulation arm is... The process then includes: combining the first optical carrier and the second optical carrier, whose phase bias point has been adjusted by the modulator, via the modulator's coupler, and then converting them into a photocurrent input spectrum analyzer via the photodetector.

[0008] According to some embodiments of this disclosure, the above-mentioned processing of the frequency components of the beat frequency signals of the plurality of first optical carriers and the second optical carriers using a first predetermined function corresponding to the photodetector to obtain a first frequency response includes: based on the first optical carriers and the second optical carriers, measuring the frequency components of the beat frequency signals of the first optical carriers and the second optical carriers contained in the output signal of the spectrum analyzer; and comparing the component of the sum of the frequencies of the beat frequency signals of the first optical carriers and the second optical carriers with the component of the frequency difference between the beat frequency signals of the first optical carriers and the second optical carriers to obtain the first frequency response.

[0009] According to some embodiments of this disclosure, the method of comparing the component of the sum of the frequencies of the beat frequency signals of the first optical carrier and the second optical carrier with the component of the frequency difference between the beat frequency signals of the first optical carrier and the second optical carrier to obtain the first frequency response includes: multiplying the component of the sum of the frequencies of the beat frequency signals of all the first optical carrier and the second optical carrier with the component of the frequency difference between the beat frequency signals of the first optical carrier and the second optical carrier to obtain the first frequency response.

[0010] According to some embodiments of this disclosure, the above-mentioned processing of the frequency components of the beat frequency signals of the plurality of first optical carriers and the second optical carriers using a second predetermined function corresponding to the photonic integrated chip to obtain a second frequency response includes: based on the first optical carriers and the second optical carriers, measuring the frequency components of the beat frequency signals of the first optical carriers and the second optical carriers contained in the output signal of the spectrum analyzer; and comparing the harmonic frequency component of the beat frequency signals of the first optical carriers and the second optical carriers with predetermined parameters with the frequency difference component of the beat frequency signals of the first optical carriers and the second optical carriers with predetermined parameters to obtain the second frequency response.

[0011] According to some embodiments of this disclosure, the above-mentioned comparison of the frequency harmonics of the beat frequency signals of the first optical carrier with predetermined parameters and the second optical carrier with predetermined parameters, and the frequency difference component of the beat frequency signals of the first optical carrier with predetermined parameters and the second optical carrier with predetermined parameters, to obtain the second frequency response includes: multiplying the comparison of the frequency harmonics of the beat frequency signals of the first optical carrier with predetermined parameters and the second optical carrier with predetermined parameters, and the frequency difference component of the beat frequency signals of the first optical carrier with predetermined parameters and the second optical carrier with predetermined parameters, to obtain the second frequency response.

[0012] According to some embodiments of another aspect of this disclosure, an apparatus for measuring the relative frequency response of a photonic integrated chip and a photodetector is suitable for implementing the above-described method. The apparatus includes: a photonic integrated chip comprising: a laser adapted to output an optical signal; an optical coupler adapted to receive the optical signal and split the optical signal into two paths to obtain a first optical signal and a second optical signal; and a modulator comprising: a first modulation arm including a first differential electrode, the first modulation arm being adapted to receive the first optical signal and apply a sweep frequency signal to the first differential electrode using an external sweep frequency microwave source to obtain a first optical carrier modulated and output by the first modulation arm; and a second modulation arm including a second differential electrode. The second modulation arm is adapted to receive the second optical signal and apply a second radio frequency signal of fixed frequency to the second differential electrode through an external microwave source to obtain a second optical carrier modulated by the second modulation arm; wherein, a DC bias voltage is applied to the first modulation arm and the second modulation arm through an external DC voltage source to adjust the bias point of the phase of the modulator, thereby generating a phase shift; and a data acquisition module, including: a photodetector adapted to convert the first optical carrier and the second optical carrier, which are modulated and combined from the modulator, into photocurrent through square-law detection; and a spectrum analyzer adapted to detect the microwave signal after the first optical carrier and the second optical carrier beat frequency.

[0013] According to some embodiments of this disclosure, both the first modulation arm and the second modulation arm are provided with bias electrodes.

[0014] According to some embodiments of this disclosure, the apparatus for measuring the relative frequency response of a photonic integrated chip and a photodetector further includes a control module adapted to control the sweep microwave source, the microwave source, and the DC voltage source.

[0015] According to an embodiment of this disclosure, a method and apparatus for measuring the relative frequency response of a photonic integrated chip and a photodetector are disclosed. The method involves sweeping a first radio frequency signal loaded on the first modulation arm of a modulator in response to a sweep signal applied externally to the first modulation arm, thereby obtaining multiple first optical carriers modulated by the first modulation arm. A second optical carrier modulated by the second modulation arm is obtained in response to a second radio frequency signal of a fixed frequency applied externally to the second modulation arm. An external DC voltage source is used to adjust the phase bias point of the modulator so that the difference in phase shift between the first and second modulation arms is equal to... Based on the frequency components of the beat frequency signals of multiple first optical carriers and second optical carriers, a first frequency response is obtained by processing the frequency components of the predetermined beat frequency signals using a first predetermined function corresponding to the photodetector; based on the frequency components of the beat frequency signals of multiple first optical carriers and second optical carriers, a second frequency response is obtained by processing the frequency components of the predetermined beat frequency signals using a second predetermined function corresponding to the photonic integrated chip. This allows for the simultaneous measurement of the relative frequency response of the photonic integrated chip and the photodetector, achieving high-resolution frequency response measurement while performing self-calibration using the first and second frequency responses. Attached Figure Description

[0016] Figure 1 This is a flowchart illustrating a method for measuring the relative frequency response of a photonic integrated chip and a photodetector according to an illustrative embodiment of the present disclosure; and

[0017] Figure 2 This is a diagram of an apparatus for measuring the relative frequency response of a photonic integrated chip and a photodetector according to an illustrative embodiment of the present disclosure. Detailed Implementation

[0018] The embodiments of the present disclosure will now be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the disclosure. In the following detailed description, numerous specific details are set forth to provide a thorough understanding of the embodiments of the present disclosure for ease of explanation. However, it will be apparent that one or more embodiments may be practiced without these specific details. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concepts of the present disclosure.

[0019] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit this disclosure. The terms “comprising,” “including,” etc., as used herein indicate the presence of the stated features, steps, operations, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, or components.

[0020] All terms used herein (including technical and scientific terms) have the meanings commonly understood by those skilled in the art, unless otherwise defined. It should be noted that the terms used herein are to be interpreted in a manner consistent with the context of this specification, and not in an idealized or overly rigid way.

[0021] When using expressions such as "at least one of A, B, and C", they should generally be interpreted in accordance with the meaning that is commonly understood by a person skilled in the art (e.g., "a system having at least one of A, B, and C" should include, but is not limited to, a system having A alone, a system having B alone, a system having C alone, a system having A and B, a system having A and C, a system having B and C, and / or a system having A, B, and C, etc.).

[0022] To address the problem in existing technologies that cannot simultaneously measure the relative frequency response of a photonic integrated chip and a photodetector, according to one aspect of the inventive concept of this disclosure, a first radio frequency signal loaded on the first modulation arm is swept and output in response to a sweep signal applied externally to the first modulation arm of the modulator, resulting in multiple first optical carriers modulated and output by the first modulation arm; a second optical carrier is modulated and output by the second modulation arm in response to a second radio frequency signal of a fixed frequency applied externally to the second modulation arm of the modulator; and the phase bias point of the modulator is adjusted by an external DC voltage source so that the difference in phase shift generated by the first modulation arm and the second modulation arm is... Based on the frequency components of the beat frequency signals of multiple first optical carriers and second optical carriers, a first frequency response is obtained by processing them using a first predetermined function corresponding to the photodetector; based on the frequency components of the beat frequency signals of multiple first optical carriers and second optical carriers, a second frequency response is obtained by processing them using a second predetermined function corresponding to the photonic integrated chip. This allows for the simultaneous measurement of the relative frequency response of the photonic integrated chip and the photodetector, achieving high-resolution frequency response measurement while performing self-calibration using the first and second frequency responses.

[0023] Figure 1 This is a flowchart of a method for measuring the relative frequency response of a photonic integrated chip and a photodetector according to an illustrative embodiment of the present disclosure.

[0024] According to embodiments of this disclosure, such as Figure 1As shown, a method for measuring the relative frequency response of a photonic integrated chip and a photodetector is provided. The photonic integrated chip includes a modulator, and the method for measuring the relative frequency response of the photonic integrated chip and the photodetector includes the following steps S1 to S5.

[0025] Step S1: In response to the sweep signal applied externally to the first modulation arm of the modulator, the first radio frequency signal loaded on the first modulation arm is swept and output to obtain multiple first optical carriers modulated and output by the first modulation arm.

[0026] According to embodiments of this disclosure, the optical signal E output by the laser... in (t) is split into two paths by the optical coupler and enters the first modulation arm and the second modulation arm of the modulator.

[0027] According to embodiments of this disclosure, the optical field of the optical signal input to the modulator can be represented by the following formula (1):

[0028] E in (t)=E in exp(jω c t) (1)

[0029] Among them, E in Represented as the amplitude of the optical signal, ω c Let ω represent the angular frequency of the optical signal, j represent the Jacobian coefficient, and t represent time.

[0030] According to optional embodiments of this disclosure, the modulator may be selected, for example, a Mach-Zehnder modulator.

[0031] According to an optional embodiment of this disclosure, the sweep signal is applied to the first modulation arm of the modulator by an external microwave vector network analyzer, which applies the sweep signal through a microwave probe.

[0032] Step S2: In response to a second radio frequency signal of a fixed frequency applied externally to the second modulation arm of the modulator, a second optical carrier modulated and output by the second modulation arm is obtained.

[0033] According to an optional embodiment of this disclosure, a fixed-frequency microwave signal is applied to the second modulation arm of the modulator via an external microwave source.

[0034] According to embodiments of this disclosure, the microwave signal V(t) can be represented by the following formula (2):

[0035]

[0036] Among them, V RF Represented as the amplitude of the radio frequency signal, ω RF The angular frequency ω of the radio frequency signal is expressed as follows: RF=2πf RF , This is represented as the phase of the radio frequency signal.

[0037] Step S3: Adjust the phase bias point of the modulator using an external DC voltage source so that the phase shift difference between the first and second modulation arms is [value missing].

[0038] According to embodiments of this disclosure, an external DC voltage source controls the phase bias point of the modulator via a DC probe.

[0039] According to embodiments of this disclosure, the optical signal E output after modulation by the modulator MZM (t) can be expressed by the following formula (3):

[0040]

[0041] Where, ω RF1 It is expressed as the angular frequency of the first radio frequency signal loaded on the first modulation arm. The phase of the first radio frequency signal, ω RF1 It is expressed as the angular frequency of the second radio frequency signal loaded on the second modulation arm. This is represented by the phase of the second radio frequency signal. This is represented by the thermally modulated phase shift generated by adjusting the DC bias voltage source of the first modulation arm. This represents the thermally modulated phase shift generated by the adjustment of the second modulation arm through the DC bias voltage source, where m represents the modulation depth of the modulator. This is represented as the modulation depth on the first modulation arm. V represents the modulation depth on the second modulation arm. RF1 V represents the amplitude of the first radio frequency signal. RF2 V represents the amplitude of the second radio frequency signal. π It is represented as half-wave voltage.

[0042] According to embodiments of this disclosure, formula (3) after Euler transformation can be expressed by the following formula (4):

[0043]

[0044] According to embodiments of this disclosure, the phase bias point of the modulator is adjusted so that the modulator operates at its minimum operating point, such that the difference in phase shift between the first and second modulation arms is... This generates carrier-suppressed single-sideband modulation.

[0045] Step S4: Based on the frequency components of the beat frequency signals of multiple first optical carriers and second optical carriers, process them using a first predetermined function corresponding to the photodetector to obtain a first frequency response.

[0046] Step S5: Based on the frequency components of the beat frequency signals of multiple first optical carriers and second optical carriers, process them using a second predetermined function corresponding to the photonic integrated chip to obtain a second frequency response.

[0047] According to embodiments of this disclosure, a first radio frequency signal loaded on the first modulation arm is swept and output in response to a sweep signal applied externally to the first modulation arm of the modulator, resulting in a plurality of first optical carriers modulated by the first modulation arm; a second optical carrier is modulated by the second modulation arm in response to a second radio frequency signal of a fixed frequency applied externally to the second modulation arm of the modulator; and the phase bias point of the modulator is adjusted by an external DC voltage source so that the difference in phase shift generated by the first modulation arm and the second modulation arm is... Based on the frequency components of the beat frequency signals of multiple first optical carriers and second optical carriers, a first frequency response is obtained by processing them using a first predetermined function corresponding to the photodetector; based on the frequency components of the beat frequency signals of multiple first optical carriers and second optical carriers, a second frequency response is obtained by processing them using a second predetermined function corresponding to the photonic integrated chip. This allows for the simultaneous measurement of the relative frequency response of the photonic integrated chip and the photodetector, achieving high-resolution frequency response measurement while performing self-calibration using the first and second frequency responses.

[0048] According to an embodiment of this disclosure, the sweep frequency of the first radio frequency signal applied to the first modulation arm is n times the frequency of the second radio frequency signal applied to the second modulation arm, where n is an integer not less than 1.

[0049] According to an embodiment of this disclosure, the sweep frequency of the first radio frequency signal is f1, and the frequency of the fixed-frequency microwave signal is f2. The relationship between f1 and f2 can be expressed by the following formula (5):

[0050] f1 = n * f2 (5).

[0051] According to an embodiment of this disclosure, a microwave vector network analyzer is applied to the first modulation arm of the modulator to perform a frequency sweep output. The frequency sweep frequency of the first radio frequency signal is n times the frequency of the second radio frequency signal, where n is an integer not less than 1. In subsequent operations, the ratio of the frequency response of the photodetector at multiple frequency points with fixed frequency intervals can be obtained, thus expanding the measurement range.

[0052] According to embodiments of this disclosure, the phase bias point of the modulator is adjusted by an external DC voltage source so that the difference in phase shift generated by the first modulation arm and the second modulation arm is... The process then includes: combining the first and second optical carriers, whose phase bias points have been adjusted by the modulator, and then combining them again via the modulator's upper coupler. After being detected by the square law of the photodetector, the combined optical carriers are converted into a photocurrent input spectrum analyzer.

[0053] According to an embodiment of this disclosure, the first optical carrier and the second optical carrier, whose phase bias point has been adjusted by the modulator, are combined and input into a photodetector. After square-law detection, the photocurrent is output, and then the microwave signal obtained by the beat frequency is detected by a spectrum analyzer. Ignoring higher-order terms, the microwave signal can be represented by the following formula (6):

[0054]

[0055] Where R(f) represents the frequency response of the photodetector. This is expressed as the thermally modulated phase shift difference between the first and second modulation arms of the modulator. This is represented by the thermally modulated phase shift of the first modulation arm. ω1 represents the thermally modulated phase shift of the second modulation arm, ω2 represents the angular frequency of the first radio frequency signal applied to the first modulation arm, and ω3 represents the angular frequency of the second radio frequency signal applied to the second modulation arm.

[0056] According to embodiments of this disclosure, using the Jacobi-Angel identity, formula (6) can be transformed into the following formula (7):

[0057]

[0058] According to embodiments of this disclosure, the bias point of the modulator's phase is adjusted so that the modulator operates at its minimum operating point. for Carrier-suppressed single-sideband modulation is generated, and equation (7) can be expressed by the following equation (8):

[0059]

[0060] According to embodiments of this disclosure, processing the frequency components of the beat frequency signals of a plurality of first optical carriers and second optical carriers using a first predetermined function corresponding to a photodetector to obtain a first frequency response includes: measuring the frequency components of the beat frequency signals of the first optical carriers and second optical carriers contained in the output signal of the spectrum analyzer based on the first optical carriers and second optical carriers; and comparing the component of the sum of the frequencies of the beat frequency signals of the first optical carriers and second optical carriers with the component of the frequency difference between the beat frequency signals of the first optical carriers and second optical carriers to obtain the first frequency response.

[0061] According to an embodiment of the present disclosure, based on a first optical carrier and a second optical carrier, the output signal of the spectrum analyzer is measured to contain a radio frequency signal of a predetermined frequency obtained by beating the first optical carrier and the second optical carrier (Formula (8)).

[0062] According to embodiments of this disclosure, the component of the sum of frequencies in the beat frequency signals of the first optical carrier and the second optical carrier is compared with the component of the frequency difference in the beat frequency signals of the first optical carrier and the second optical carrier, that is, the component containing the two angular frequency components ω1+ω2 and ω1-ω2 is compared to obtain the first frequency response characterizing the photodetector, which can be expressed by the following formula (9):

[0063]

[0064] According to an optional embodiment of this disclosure, taking an output frequency f1 = (2n+1)f2, n = 1, 2, 3… as an example, while achieving a wide bandwidth, the ratios of the frequency responses of the photodetectors at multiple frequency points spaced 2*f2 can be obtained, respectively.

[0065] According to embodiments of this disclosure, comparing the component of the sum of frequencies of the beat frequency signals of the first optical carrier and the second optical carrier with the component of the frequency difference between the beat frequency signals of the first optical carrier and the second optical carrier to obtain a first frequency response includes: multiplying the component of the sum of frequencies of all the beat frequency signals of the first optical carrier and the second optical carrier with the component of the frequency difference between the beat frequency signals of the first optical carrier and the second optical carrier to obtain a first frequency response.

[0066] According to embodiments of this disclosure, by multiplying the component of the sum of frequencies in the beat frequency signals of all the first and second optical carriers with the component of the frequency difference in the beat frequency signals of the first and second optical carriers, the frequency response of different frequency points relative to f2 can be obtained, thereby improving the measurement accuracy.

[0067] According to embodiments of this disclosure, a second frequency response is obtained by processing the frequency components of the beat frequency signals of a plurality of first and second optical carriers using a second predetermined function corresponding to a photonic integrated chip. This includes: measuring the frequency components of the beat frequency signals of the first and second optical carriers contained in the output signal of the spectrum analyzer, based on the first and second optical carriers. The second frequency response is obtained by comparing the harmonic frequency components of the beat frequency signals of the first and second optical carriers with predetermined parameters with the frequency difference components of the beat frequency signals of the first and second optical carriers with predetermined parameters.

[0068] According to an embodiment of the present disclosure, based on a first optical carrier and a second optical carrier, a radio frequency signal (equation (8)) containing a predetermined frequency component obtained by beating the first optical carrier and the second optical carrier is measured in the output signal of the spectrum analyzer.

[0069] According to embodiments of this disclosure, the frequency components of the beat frequency signals of the first optical carrier with predetermined parameters and the second optical carrier with predetermined parameters are compared with the components of the frequency difference between the beat frequency signals of the first optical carrier with predetermined parameters and the second optical carrier with predetermined parameters, that is, the components containing two angular frequency components, 2ω1 and 2(ω1-ω2), to obtain the second frequency response characterizing the modulator, which can be expressed by the following formula (10):

[0070]

[0071] According to an optional embodiment of this disclosure, taking the output frequency f1 = nf2, n = 2, 3, 4… as an example, a wide bandwidth can be achieved while obtaining the ratio of microwave signals at different frequency points, respectively.

[0072]

[0073] According to embodiments of this disclosure, comparing the frequency harmonics of the beat frequency signals of a first optical carrier with predetermined parameters and a second optical carrier with predetermined parameters, with the frequency difference component of the beat frequency signals of the first optical carrier with predetermined parameters and the second optical carrier with predetermined parameters, to obtain a second frequency response includes: multiplying the frequency harmonics of the beat frequency signals of the first optical carrier with predetermined parameters and the frequency difference component of the beat frequency signals of the second optical carrier with predetermined parameters, to obtain a second frequency response.

[0074] According to embodiments of this disclosure, the frequency response R(f) of the photodetector is used. By comparing and multiplying the frequency components of the beat frequency signals of the first optical carrier with predetermined parameters and the beat frequency signals of the second optical carrier with predetermined parameters with the frequency difference components of the beat frequency signals of the first optical carrier with predetermined parameters and the second optical carrier with predetermined parameters, the frequency response of different frequency points relative to f2 can be obtained. At the same time, the relative frequency response of the photonic integrated chip and the photodetector is measured, which improves the measurement accuracy and realizes high-resolution frequency response measurement while using the first frequency response and the second frequency response for self-calibration.

[0075] Figure 2 This is a diagram of an apparatus for measuring the relative frequency response of a photonic integrated chip and a photodetector according to an illustrative embodiment of the present disclosure.

[0076] According to another embodiment of this disclosure, such as Figure 2As shown, an apparatus for measuring the relative frequency response of a photonic integrated chip and a photodetector is suitable for implementing the above-described method. The apparatus includes a photonic integrated chip and a data acquisition module. The photonic integrated chip includes a laser, an optical coupler, and a modulator. The laser is suitable for outputting optical signals. The optical coupler is suitable for receiving optical signals and splitting them into two paths to obtain a first optical signal and a second optical signal. The modulator includes a first modulation arm and a second modulation arm. The first modulation arm includes a first differential electrode and is suitable for receiving the first optical signal. A sweep frequency signal is applied to the first differential electrode by an external sweep frequency microwave source to obtain a first optical carrier modulated by the first modulation arm. The second modulation arm includes a second differential electrode and is suitable for receiving the second optical signal. A second radio frequency signal of a fixed frequency is applied to the second differential electrode by an external microwave source to obtain a second optical carrier modulated by the second modulation arm. A DC bias voltage is applied to the first and second modulation arms by an external DC voltage source to adjust the bias point of the modulator's phase, thereby generating a phase shift. The data acquisition module includes a photodetector and a spectrum analyzer. A photodetector is suitable for converting the first and second optical carriers, which are modulated and combined by a modulator, into photocurrents via square-law detection. A spectrum analyzer is suitable for detecting microwave signals after the first and second optical carriers beat.

[0077] According to optional embodiments of this disclosure, the laser source may be, for example, a continuous wave laser source.

[0078] According to embodiments of this disclosure, the first modulation arm is driven by a first differential electrode, and the second modulation arm is driven by a second differential electrode.

[0079] According to embodiments of this disclosure, in response to a sweep signal applied externally to the first modulation arm of the modulator, a first radio frequency signal loaded on the first modulation arm is swept and output to obtain multiple first optical carriers modulated by the first modulation arm. In response to a second radio frequency signal of a fixed frequency applied externally to the second modulation arm of the modulator, a second optical carrier is modulated by the second modulation arm. A microwave signal detected by a spectrum analyzer is recorded using a data acquisition module. Through data processing, the relative frequency response of the photonic integrated chip and the photodetector can be measured simultaneously, achieving high resolution while performing self-calibration using the first and second frequency responses.

[0080] According to embodiments of this disclosure, bias electrodes are provided on both the first modulation arm and the second modulation arm.

[0081] According to embodiments of this disclosure, a DC bias voltage is applied to the bias electrodes of the first and second modulation arms by an external DC voltage source to adjust the bias point of the modulator's phase, thereby generating a phase shift.

[0082] According to embodiments of this disclosure, the apparatus for measuring the relative frequency response of a photonic integrated chip and a photodetector further includes a control module adapted to control a swept microwave source, a microwave source, and a DC voltage source.

[0083] According to embodiments of this disclosure, a control module controls a frequency-sweeping microwave source to perform frequency sweep output at predetermined intervals. The control module also controls the microwave source to apply a microwave signal of a fixed frequency. Finally, the control module controls a DC voltage source to ensure the modulator operates at its minimum operating point.

[0084] According to embodiments of this disclosure, by using a control module to control the swept microwave source, microwave source, and DC voltage source in real time, frequency responses at different frequency points can be obtained.

[0085] It should also be noted that the directional terms mentioned in the embodiments, such as "up," "down," "front," "back," "left," and "right," are only for reference to the directions in the accompanying drawings and are not intended to limit the scope of protection of this disclosure. Throughout the drawings, the same elements are represented by the same or similar reference numerals. Conventional structures or constructions will be omitted where they may cause confusion in understanding this disclosure, and the shapes and dimensions of the components in the drawings do not reflect actual size and proportion, but are only schematic representations of the embodiments of this disclosure.

[0086] Unless otherwise stated, the numerical parameters in this specification and the appended claims are approximate values ​​and can be varied according to desired characteristics derived from the content of this disclosure. Specifically, all figures used in the specification and claims to indicate composition, reaction conditions, etc., should be understood to be modified by the term "about" in all cases. Generally, this means that a specific amount varies by ±10% in some embodiments, ±5% in some embodiments, ±1% in some embodiments, and ±0.5% in some embodiments.

[0087] The use of ordinal numbers such as "first," "second," "third," etc., in the specification and claims to modify the corresponding elements does not imply that the element has any ordinal number, nor does it represent the order of one element with another element, or the order of manufacturing methods. The use of these ordinal numbers is only to enable a named element to be clearly distinguished from another element with the same name.

[0088] Furthermore, unless specifically described or required to occur in a specific order, the order of the above steps is not limited to those listed above and can be varied or rearranged according to the desired design. Moreover, the above embodiments can be used in combination with each other or with other embodiments based on design and reliability considerations; that is, technical features from different embodiments can be freely combined to form more embodiments.

[0089] The embodiments of this disclosure have been described above. However, these embodiments are for illustrative purposes only and are not intended to limit the scope of this disclosure. Although various embodiments have been described above, this does not mean that the measures in the various embodiments cannot be used advantageously in combination. The scope of this disclosure is defined by the appended claims and their equivalents. Various substitutions and modifications can be made by those skilled in the art without departing from the scope of this disclosure, and all such substitutions and modifications should fall within the scope of this disclosure.

Claims

1. A method for measuring the relative frequency response of a photonic integrated chip and a photodetector, the photonic integrated chip including a modulator, the method comprising: In response to a sweep signal applied externally to the first modulation arm of the modulator, a first radio frequency signal loaded on the first modulation arm is swept and output to obtain a plurality of first optical carriers modulated and output by the first modulation arm; In response to a second radio frequency signal of a fixed frequency applied externally to the second modulation arm of the modulator, a second optical carrier modulated and output by the second modulation arm is obtained; By using an external DC voltage source, the phase bias point of the modulator is adjusted so that the difference in phase shift between the first modulation arm and the second modulation arm is... Based on the frequency components of the beat frequency signals of the multiple first optical carriers and the second optical carriers, a first frequency response is obtained by processing them using a first predetermined function corresponding to the photodetector. Based on the frequency components of the beat frequency signals of the multiple first optical carriers and the second optical carriers, a second predetermined function corresponding to the photonic integrated chip is used for processing to obtain a second frequency response.

2. The method according to claim 1, wherein, The frequency of the first radio frequency signal applied to the first modulation arm is n times the frequency of the second radio frequency signal applied to the second modulation arm, where n is an integer not less than 1.

3. The method according to claim 1, wherein, The phase bias point of the modulator is adjusted by an external DC voltage source so that the difference in phase shift between the first modulation arm and the second modulation arm is... This includes: The first optical carrier and the second optical carrier, whose phase bias point has been adjusted by the modulator, are combined by the modulator's upper coupler and then converted into a photocurrent input spectrum analyzer by the photodetector.

4. The method according to claim 3, wherein, The step of processing the frequency components of the beat frequency signals of the plurality of first optical carriers and second optical carriers using a first predetermined function corresponding to the photodetector to obtain the first frequency response includes: Based on the first optical carrier and the second optical carrier, the frequency components of the beat frequency signals of the first optical carrier and the second optical carrier are measured in the output signal of the spectrum analyzer; The first frequency response is obtained by comparing the component of the sum of the frequencies of the beat frequency signals of the first optical carrier and the second optical carrier with the component of the frequency difference between the beat frequency signals of the first optical carrier and the second optical carrier.

5. The method according to claim 4, wherein, The step of comparing the component of the sum of the frequencies of the beat frequency signals of the first optical carrier and the second optical carrier with the component of the frequency difference between the beat frequency signals of the first optical carrier and the second optical carrier to obtain the first frequency response includes: The first frequency response is obtained by multiplying the sum of the frequencies of all the beat frequency signals of the first optical carrier and the second optical carrier by the component of the frequency difference between the beat frequency signals of the first optical carrier and the second optical carrier.

6. The method according to claim 3, wherein, The step of processing the frequency components of the beat frequency signals of the plurality of first optical carriers and second optical carriers using a second predetermined function corresponding to the photonic integrated chip to obtain the second frequency response includes: Based on the first optical carrier and the second optical carrier, the frequency components of the beat frequency signals of the first optical carrier and the second optical carrier are measured in the output signal of the spectrum analyzer; The second frequency response is obtained by comparing the frequency harmonic component of the beat frequency signal of the first optical carrier with predetermined parameters and the beat frequency signal of the second optical carrier with predetermined parameters with the frequency difference component of the beat frequency signal of the first optical carrier with predetermined parameters and the second optical carrier with predetermined parameters.

7. The method according to claim 6, wherein, The step of comparing the frequency harmonic component of the beat frequency signal of the first optical carrier with predetermined parameters and the beat frequency signal of the second optical carrier with predetermined parameters with the frequency difference component of the beat frequency signal of the first optical carrier with predetermined parameters and the second optical carrier with predetermined parameters to obtain the second frequency response includes: The second frequency response is obtained by multiplying the harmonic frequency components of the beat frequency signals of the first optical carrier with all predetermined parameters and the second optical carrier with predetermined parameters with the frequency difference components of the beat frequency signals of the first optical carrier with predetermined parameters and the second optical carrier with predetermined parameters.

8. An apparatus for measuring the relative frequency response of a photonic integrated chip and a photodetector, suitable for implementing the method as described in any one of claims 1 to 7, the apparatus comprising: Photonic integrated chips, including: Lasers are used to output optical signals. An optical coupler, suitable for receiving the optical signal and splitting the optical signal into two paths to obtain a first optical signal and a second optical signal; and Modulator, including: A first modulation arm includes a first differential electrode, which is adapted to receive the first optical signal. A sweep frequency signal is applied to the first differential electrode by an external sweep frequency microwave source to obtain a first optical carrier modulated and output by the first modulation arm. The second modulation arm includes a second differential electrode. The second modulation arm is adapted to receive the second optical signal. A second radio frequency signal of a fixed frequency is applied to the second differential electrode by an external microwave source to obtain a second optical carrier modulated and output by the second modulation arm. Specifically, a DC bias voltage is applied to the first and second modulation arms by an external DC voltage source to adjust the bias point of the modulator's phase, thereby generating a phase shift; and The data acquisition module includes: A photodetector suitable for converting the first and second optical carriers, modulated and combined from the modulator, into photocurrent via square-law detection; and A spectrum analyzer is suitable for detecting microwave signals after the first optical carrier and the second optical carrier beat at the same frequency.

9. The apparatus according to claim 8, wherein, Both the first modulation arm and the second modulation arm are provided with bias electrodes.

10. The apparatus according to claim 8, wherein, Also includes: The control module is suitable for controlling the swept-frequency microwave source, the microwave source, and the DC voltage source.

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